This invention relates to a method for connecting a coated lead wire to a terminal of a coil bobbin in such a state that the coated lead wire is entwined around the terminal.
There has generally been known a method for connecting a coated lead wire to a bare lead wire (corresponding to a terminal) in a coil bobbin or the like, as disclosed in Japanese Patent Application Public Disclosure HEI 10-134925(A).
To be specific, in the conventional coil structure, the bare lead wire around which the coated lead wire is wound is previously coated with tin (Sn) serving as a bonding-assistant agent by thermal spray coating or in other ways, or applied with Sn in the form of plating or powder paste. The bare lead wire acting as a heating element is heated with Joule heat produced by being supplied with electricity to melt away the insulating coating and the tin adhered to the bare lead wire.
According to the conventional method for connection of the lead wires, the bare lead wire is in contact with the coated lead wire in such a small area that the coated lead wire cannot be covered with solder. Thus, the conventional method entailed a disadvantage such that the joining strength between the bare lead wire and the coated lead wire could not be fully increased.
Besides, the conventional method has a problem that oxidization possibly caused on the contact surface between the bare lead wire and the coated lead wire due to oxygen in the air in heating the wires interferes with desirable connection therebetween.